Various paint compositions are known for use on automotive and architectural glass. Such paints are used, for example, to form opaque borders around the peripheral marginal surfaces of glazings used as windshields, sidelites, and backlites of motor vehicles. These borders are used to obstruct from view attachment means for the glazings and protect adhesives which might be used from exposure to light which could degrade them.
Generally these compositions are ceramic compositions formed from a mixture of metal oxides in an organic (oil based) vehicle like mineral oil. The opaque peripheral marginal paint bands fired onto automotive glazings are generally black provided by colorant oxides like chrome oxide, cobalt oxide and nickel oxide. In view of environmental and commercial considerations, more desirable water-based paints have been developed for use in place of such organic vehicle paints. One such paint is disclosed in U.S. Pat. No. 5,698,026, commonly assigned herewith, which is a soda-lime silicate based paint which uses metal oxide pigment to color the glass. That water based paint advantageously is curable at relatively low temperatures compared to the relatively high temperatures generally required for ceramic/organic vehicle paint curing. Subjecting the glass to high temperatures to cure the paint can impart undesirable optical distortions into the glass sheets.
It is known in the automotive industry that the outer edge of a windshield is most sensitive to stone chips because of stresses contained in this region. Adding paint to this region, and later subjecting the glass to heating and shaping, I believe can intensify this stress, particularly weakening the glass in the painted area and making it more susceptible to stone chipping or breakage. Automotive windshields are made of two panes of glass laminated together with a layer of polyvinyl in-between. Even applying the paint to the inside glass surface near the occupant, which is not directly contacted by stones, can have a negative impact on stone chip resistance of the glass surface facing outside the vehicle.
It is an object of the present composition to provide a water-based paint composition which has improved stone chip resistance for the glass on which it is applied. It is an object of the invention to provide a water-based paint with excellent adhesion to glass on which it is applied. I have found that these objects can be accomplished by including fused silica in a water based silicate paint. These and other objects are accomplished by the present invention paint which is curable at relatively low temperatures and which exhibits excellent durability.